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In Pursuit of the Plumleaf Azalea 

Fri., Jan. 7, 2022

By Connor Ryan, MS, Rhododendron Collections Manager

An important part of my job as Rhododendron Collections Manager is seeking new plants to enhance our Rhododendron collection. As part of an ongoing thrust to collect North America’s native rhododendrons and azaleas, last month I embarked on a trip in pursuit of the plumleaf azalea (Rhododendron prunifolium). 

Growing only in the Chattahoochee River Drainage Basin on either side of the Alabama/Georgia line, the plumleaf azalea may be the rarest azalea in North America. In addition to being rare, it is also a great garden plant. It produces brick red flowers in late summer and fall, when almost no other rhododendrons (or other plants!) are blooming. Since most North American native azaleas are native to the Southeast, people often ask me if southern plants will be cold hardy for us in Ohio. I think the proof is in the (plum) pudding – we have 4 plants of this species at Holden Arboretum accessioned in 1961! These plants are of unknown origin, so I wanted to collect this species from current, wild populations in Alabama and Georgia. 

In mid-December I traveled to Auburn University’s Davis Arboretum to meet with Patrick Thompson, one of their curators. I knew Patrick from my time as a student at Auburn University and was reconnected with him by Juliana Medeiros, HF&G Plant Biologist, who is working with Patrick and another Auburn colleague on an azalea research project. Patrick was gracious enough to spend the whole week with me as we scooted around public and private sites south of Auburn. In total, we were able to visit seven sites over five days, found plumleaf azaleas at six of those sites, and were able to collect seeds at 5 of them. Seedlings will be raised for the HF&G gardens, and some seeds will be sent to the United States National Arboretum seed bank for long term conservation storage. 

Below are some photo highlights of our trip. 

On our first day we went to Providence Canyon State Park in Lumpkin, Georgia. Despite being an ecological and geological disaster (read more here), it is the premiere site for plumleaf azaleas. They even made it onto the Georgia U-Haul! Exposed soil from nearly 2 centuries of erosion following poor agricultural and forestry practices has led to a network of canyons that are growing larger by the day. Plumleaf azaleas naturally occur here and have been colonizing the eroding spaces, creating a spectacular summer show.  

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Following a fruitful day in Providence Canyon, literally – we collected many seed-bearing azalea fruits called capsules, we spent the remainder of the week chasing down potential sites shared with us by a mutual colleague Ron Miller. In most cases we had a general idea of where to look but would need to search each site for the plants.

The plumleaf azaleas are most frequently found on steep, ankle-breaker slopes above clearwater streams. It is not a hard and fast rule, but the slopes were usually north-facing, and the plants would only be on one side of the stream.  

While deciduous azaleas can be difficult to identify out of bloom, plumleaf azaleas have distinctly hairless vegetative and flower buds and long, plump fruits. Plants can easily be 15’ x 15’ or larger, as shown here in Henry County, AL, with Patrick for scale. 
Plants commonly encountered alongside the plumleaf azaleas were American beech (Fagus grandifolia), big leaf magnolia (Magnolia macrophylla), bluff oak (Quercus austrina) coastal doghobble (Leucothoe axillaris), dwarf rhododendron (Rhododendron minus) mountain laurel (Kalmia latifolia), oakleaf hydrangea (Hydrangea quercifolia), and ferns galore. I was delighted to see so many beloved garden plants growing wild in the same place.  

We encountered some fungal friends along the way as well, including lion’s mane mushrooms five days in a row! Of course we had to eat them! Finds on separate days pictured below. 

On our third day, after visiting two populations of plumleaf azaleas in Lee County, AL, with almost no seed available to collect, we took a quick canoe ride along Halawakee Creek in search of the sweet azalea, Rhododendron arborescens. This particular form of sweet azalea is unique in that it blooms in fall rather than spring. Azalea aficionados often call this Rhododendron arborescens var. georgiana, though that is not an officially recognized name at present. 

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Other highlights of the trip include the world’s first drive-thru art museum, an abandoned moonshine still, and a flock of pet turkeys. So many things to see and do, and I’m grateful for these opportunity afforded to me as an HF&G staff member. 

And of course, the people we interacted with and helped us along the way made the trip worthwhile. Many thanks to the Bain family, Glenn Bracewell, Anu Goedhart, Adam Hardy, Elaine and Thomas Kennedy, Lisa Kruse, Brian Nichols, Juliana Medeiros, Ron Miller, Jimmy Rane, Spencer Roy, Patrick Thompson, John Torbert, and Elias Watson who helped make this trip possible.  

We’ve only cracked the surface searching for plumleaf azaleas, and I hope to return soon. Below is our finest plumleaf azalea at HF&G. I can’t wait to have more of these on the grounds so that they can serve our scientific, conservation, horticultural, and educational mission. 

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Connor Ryan, MS

Connor Ryan, MS

Rhododendron Collections Manager

As the Rhododendron Collections Manager at Holden Forests & Gardens (HF&G), my job is to curate and build the Rhododendron collections across all three HF&G campuses. The genus Rhododendron, which consists of roughly 1,000 total species, contains four groups of plants significant to Northeast Ohio: evergreen azaleas, deciduous azaleas, large leaf rhododendrons and small leaf rhododendrons. This diversity, coupled with the ability of species to freely hybridize within their respective groups, provides ample opportunities to collect and display an array of interesting and rare rhododendrons from around the world. During the growing season, I am most frequently found at the David G. Leach Research Station, a 30-acre facility dedicated to Rhododendron breeding, evaluation, and display in Madison, Ohio. I am actively involved in the Rhododendron breeding program at HFG started by David G. Leach, PhD, and continued by Steve Krebs, PhD. I am interested in ex-situ plant conservation, ornamental plant breeding and evaluation, and plant propagation. Feel free to reach out if you are interested in collaborating or if you want to talk plants.

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